Classifications

• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
  • C03C3/00—Glass compositions
  • C03C3/04—Glass compositions containing silica
  • C03C3/076—Glass compositions containing silica with 40% to 90% silica, by weight
  • C03C3/083—Glass compositions containing silica with 40% to 90% silica, by weight containing aluminium oxide or an iron compound
  • C03C3/085—Glass compositions containing silica with 40% to 90% silica, by weight containing aluminium oxide or an iron compound containing an oxide of a divalent metal
  • C03C3/087—Glass compositions containing silica with 40% to 90% silica, by weight containing aluminium oxide or an iron compound containing an oxide of a divalent metal containing calcium oxide, e.g. common sheet or container glass
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
  • C03C3/00—Glass compositions
  • C03C3/04—Glass compositions containing silica
  • C03C3/076—Glass compositions containing silica with 40% to 90% silica, by weight
  • C03C3/095—Glass compositions containing silica with 40% to 90% silica, by weight containing rare earths
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
  • C03C3/00—Glass compositions
  • C03C3/04—Glass compositions containing silica
  • C03C3/076—Glass compositions containing silica with 40% to 90% silica, by weight
  • C03C3/102—Glass compositions containing silica with 40% to 90% silica, by weight containing lead
  • C03C3/105—Glass compositions containing silica with 40% to 90% silica, by weight containing lead containing aluminium

Definitions

• a glass composition includes PbO falling at the range 2 Filed; Dec. 12, 2 of 0,5 to 3% by weight as a component for absorbing the X-rays, and particularly, the glass composition is [21] Appl- N03 314,420 capable of including amount :more than 1% without the discoloration due to the electron beams.
• CeO is [30] Foreign Appncation Priority Data added to the glass composition to compensate PbO for Dec 20 1971 J3 an 46402574 the discoloration due to the irradiation of the X-rays, p and the amount of CeO is selected at the range of 0,2
• the total amount of the X-ray, absorption com- UNITED STATES PATENTS ponents is more than 15% by weight to maintain the 3,356,579 12/1967 Harrington 106/53 B d t r in d valu of the X-ray absorption coeffici- 3.369,961 2/1968 Dalton et al. 106/53 B 3,464,932 9/1969 Connelly et al 106/53 B 3,619,219 11/1971 Bromer et a1 252/478 X 9 Claims, N0 Drawings GLASS COMPOSITION
• This invention relates to a glass composition which is suitable for a panel glass of a color television tube.
• the glass composition of this type should be necessary to have various properties to be satisfied therein before and after forming the panel glass of the color television tube.
• the glass composition is molded into the panel glass for the color television tube with a high accuracy after it is molten during a heat treatment and thereafter, the panel glass formed is sealed to a funnel portion through the sealing step. Accordingly, before the molding process of the panel glass, the glass composition is required to have such properties that seeds (bubbles) will readily burst to be free from the molten material during the melting step, striae (cords) are hardly formed and it can readily be molded. Especially, it is required to perform the molding process smoothly that a temperature of liquid phase of the glass composition is less than 880C.
• the glass composition should necessarily possess a strain point more than 450C for preventing the curvature of the inner surface of the panel glass from varying by softening during the sealing process. Moreover, it is necessary that the composition should have an average coefficient of thermal expansion of 98 X to 102 X 10' cm/cmC within a temperature range of 30 to 380C. Still further, in case the panel glass dissolves a good deal in the HF solution during the preparation, the glass turns opaque and adherence of a phosphor to be coated on the glass surface is diluted thereby.
• the glass composition of this type should be required to have the excellent optical properties against various kinds of rays. That is, since on the panel glass, a clear image should be reproduced with a good contrast and a natural color on a color television, severe conditions are imposed on the panel glass with respect to the optical transmission ratio and the chromaticity.
• the panel glass in general, under irradiation of X- rays, electron beams, ultraviolet rays and the like, a glass is discolored into brown or black or yellow. Therefore, the panel glass must have a property against the discoloration due to various kinds of rays. In other words, the panel glass is necessary to be discolored as little as possible. If this condition is not satisfied, it is impossible to reproduce an image of a natural color on a panel glass. Further, since X-rays occur due to bombardments of electron beams to a shadow mask, a luminescent film ofa phosphor, a panel glass or the like, the panel glass should necessarily have an ability to absorb Xrays sufficiently.
• PbO is a glass composition which is one of the good absorbers of the Xrays.
• PhD is discolored under irradiation of X-rays, and therefore, PbO is generally used in combination with CeO
• a glass composi tion containg more than 1% of PbO is not suitable for a panel glass of a color television tube.
• An object of this invention is to provide a glass composition for use as a panel glass which is free from discoloration due to irradiation of various kinds of rays, e.g. X-rays, electron beams, and ultraviolet rays, and which has good optical properties.
• various kinds of rays e.g. X-rays, electron beams, and ultraviolet rays, and which has good optical properties.
• This invention is based on the concept that it is very rare that electron beams are directly irradiated to the panel glass of the color television tube.
• the panel glass of the color television tube has a luminescent film of a phosphor coated on the inner face thereof. Therefore, electron beams at first impinge against this luminescent film and thereafter reach the glass surface. Accordingly, large parts of electron are shielded by the luminescent film, and only small partsof electron beams directly reach the glass surface after passing through the film.
• the discoloration due to electron beams in the glass containing PbO is unlike the discoloration due to X-rays.
• the former is caused by a thin layer formed on the glass surface by reduction of PbO.
• the amount of electron beams reaching the glass surface are very small as described above, it has been found that no reduced layer is formed thereon and the glass is not substantially discolored due to electron beams, if the addition of PbO is up to 3% by weight.
• the glass composition of this invention comprises 58-66% of Si() 1-4% of A1 0 6l57c of K 0, 2-8% of Na O, 0.54% of CaO, 10-18% of BaO, 0.l-4% of W0 05-13% of PhD and 01-06% of CeO and according to need, up to 2% of MgO and up to 4.5% of SrO are added thereto.
• the glass composition such as mentioned above is readily melted and the liquid phase temperature of the glass composition is below 880C (about 810 to 830C in many cases) it can be easily molded during the forming process. Further, such glass has an average value of the coefficient of thermal expansion of 98 X 10 to 102 X l0 cm/cmC within a. temperature range of from to 380C and a distortion point more than 450C, and is'excellent in resistance against hydrofluoric acid. Moreover, the glass has the excellent optical properties because it has a high :ability to absorb X-rays and hardly undergoes the discoloration under the irradiation of electron rays, X-rays and ultraviolet rays.
• the absorption coefficient (IL/Cm) to an X-ray of a wavelength of 0.6 A can be calculated from the mass absorption coefficient of glassconstituting oxides and the glass density. Therefore, in the Table are shown both the calculated and measured values of the absorption coefficient.
• each sample glass undergoes the irradiation of X-rays for 20 minutes from an X-ray tube lamp which is disposed 5cm apart from the sample glass and to which an electric current of 20mA is applied under 35KV.
• the percent transmission of the glass is measured.
• the degree of discoloration by X-rays is expressed by the difference between the percent transmission before the irradiation and that after the irradiation.
• samples 1-10 are value but in samples l-10 each of the calculated values of the absorption coefficient exceeds 20 a/cm and each of the measured values exceeds 19 p/cm, while in sample 1 l the calculated value is 19.4 p./cm and the measured value is 17.0 /cm.
• the absorption coefficient of the commercially available glass is lower than that of the glass composition of this invention with respect to either the calculated value or the measured value.
• the degree of discoloration by either X-rays or electron beams does not exceed 22%. Samples l-l0 all satisfies this requirement, but sample 1 l is insufficient in this point.
• Each of samples 3 and 5-10 contains an equal amount 0.3% of CeO:, respectively, but each of them contains a different amount of PbO which is not less than 0.7%, respectively.
• the degree of discoloration is almost equal and is within a range of 13 to 14%. Accordingly, even if the amount of PbO is increased within a range not exceeding 3%, it is possible to obtain a glass for a color television tube.
• a shadow mask is mounted inside a panel glass in advance before the irradiation of electron beams. Therefore, the inside surface of each panel glass is provided with a phosphor layer, a lacquer and an aluminum layer evaporated in vacuum before the shadow mask is mounted thereto. Thereafter, electron beams are irradiated to such an assembly under a state in practical use ofthe color television tube (except that the supplied voltage is raised up to 3OKV and the current density per unit area is also elevated to 15 A/cm Electron beams at first impinge against the shadow mask, the phosphor dots and the like to irradiate X-rays before bombarding to the panel glass.
• Patent is inferior to the glass of this invention in the property before the molding process. That is, the former takes a long time for seeds to be free from liquid of the glass composition in comparison with the latter and the temperature of the liquid phase of the former is higher than that of the latter, as shown in Table 2. Therefore, the glass of the U.S. Patent involves problems about the optical properties and the moldability.
• Table 2 Average period till seeds-free state (hour) Amount of F added Glass of this Commercially avail- (71 by weight) invention ahle SrO glass 1.2 7 10 0.8 9 12 0.2 l2 15 O l3 l7 Liquid phase temperature (C) 810-880 860-920 Referring to Table 2, there are also shown data of glass compositions obtained by adding to the sample glasses 0.2%, 0.8% or 1.2% of F.
• the glass of this invention has a lower liquid phase temperature and turns rapidly into seeds-free state and is excellent in moldability.
• the glass composition of this invention will be now restricted by the following reasons.
• the percent transmission (the transmission ratio) and chromaticity of the panel glass for the color television tube depend on BaO, W0 PbO and SrO, and therefore, they are called the main components for shielding X-rays. But the transmission ratio and the chromaticity are influenced by the content of Fe O incorporated as an impure substance. For these reasons, as is well-known in the art, the K o/Na O ratio is adjusted by suitably incorporating C00 and NiO.
• BaO, PbO and W0 should be contained in amounts of 10-1 8%, O.53% and 0.14%, respectively. More specifically, in case BaO is greater than 18%, the glass tends to devitrify easily. in case PbO exceeds 3%, the degree of brownish discoloration during the actuation of a color television tube becomes too high.
• the glass of this invention has such merits on the preparation steps as excellent melt- Wt. percent ing characteristics and moldability.
• W03 the glass of this invention has merits on the characteris- 22% if; tics, such as a sufficient X-ray absorption coefficient 10 and a very low degree of discoloration due to X-rays
• a glass composition of claim 1 consisting of:
• the glass of this invention has very effective characteristic properties as a panel glass for a color television tube. Wt. percent What is claimed is:
• a glass composition consisting essentially of, by Q 8 5:? weight, 58-66% of SiO l-4% of A1 0 6-1 5% of 0, N3 0 7.2 2-8% of Na O, 0.5-4% of CaO, 10-18% of BaO, E 0.1-4% of wo 0.5-3% of PhD, 0. l-0.6% of C60,, up 5 to 2% of MgO, up to 4.5% of SrO, and the sum of PbO, PbO BaO, W0 and SrO being more than 15%. :18 3:2
• a glass composition of claim 1 consisting of: C60 0.3;
• a glass composition of claim 1 consisting of:

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• Chemical & Material Sciences (AREA)
• Life Sciences & Earth Sciences (AREA)
• Engineering & Computer Science (AREA)
• Chemical Kinetics & Catalysis (AREA)
• General Chemical & Material Sciences (AREA)
• Geochemistry & Mineralogy (AREA)
• Materials Engineering (AREA)
• Organic Chemistry (AREA)
• Glass Compositions (AREA)
• Vessels, Lead-In Wires, Accessory Apparatuses For Cathode-Ray Tubes (AREA)

Applications Claiming Priority (1)

Publications (1)

Family

ID=14330982

Family Applications (1)

Country Status (7)

Cited By (7)

Citations (6)

Family Cites Families (1)

• 1971
  • 1971-12-20 JP JP46102574A patent/JPS5137659B2/ja not_active Expired
• 1972
  • 1972-12-11 DE DE2260535A patent/DE2260535C3/de not_active Expired
  • 1972-12-12 US US314420A patent/US3907584A/en not_active Expired - Lifetime
  • 1972-12-13 IT IT32851/72A patent/IT971819B/it active
  • 1972-12-19 NL NL7217267A patent/NL7217267A/xx not_active Application Discontinuation
  • 1972-12-20 GB GB5876372A patent/GB1418303A/en not_active Expired
  • 1972-12-20 FR FR7245459A patent/FR2164752B1/fr not_active Expired

Patent Citations (6)

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